The present invention relates to flat heat exchange tubes for use in heat exchangers such as condensers for car air conditioners and condensers for room air conditioners.
In this specification, the direction of flow of a fluid through the flat heat exchange tube will be referred to as the forward or rearward direction, or longitudinal direction, the widthwise direction of the tube orthogonal to this direction as the leftward or rightward direction, or transverse direction, and the direction of thickness of the tube as the upward or downward direction. Stated with reference to some of the drawings, the upper and lower sides and the left-and right-hand sides of FIGS. 1 and 7 will be referred to as xe2x80x9cupper and lowerxe2x80x9d and xe2x80x9cleft and right,xe2x80x9d respectively, the left-hand side of FIGS. 3 and 9 (the upper side of FIGS. 4 to 6 and FIGS. 10 to 13) as xe2x80x9cfront,xe2x80x9d and the opposite side thereof as xe2x80x9crear.xe2x80x9d Further the term xe2x80x9caluminumxe2x80x9d as used herein includes aluminum alloys in addition to pure aluminum.
In recent years, widely used in car coolers in place of conventional serpentine condensers are condensers which comprise, as shown in FIG. 14, a pair of headers 70, 71 arranged in parallel and spaced apart from each other, parallel flat heat exchange tubes 72 each joined at its opposite ends to the two headers 70, 71, corrugated aluminum fins 73 arranged in an air flow clearance between the adjacent heat exchange tubes and brazed to the adjacent tubes, an inlet pipe 74 connected to the upper end of peripheral wall of the first 70 of the headers, an outlet pipe 75 connected to the lower end of peripheral wall of the second 71 of the headers, a first partition 76 provided inside the first header 70 and positioned above the midportion thereof, and a second partition 77 provided inside the second header 71 and positioned below the midportion thereof, the number of heat exchange tubes 72 between the inlet pipe 74 and the first partition 76, the number of heat exchange tubes 72 between the first partition 76 and the second partition 77 and the number of heat exchange tubes 72 between the second partition 77 and the outlet pipe 75 decreasing from above downward. A refrigerant flowing into the inlet pipe 74 in a vapor phase flows zigzag through units of passage groups in the condenser before flowing out from the outlet pipe 75 in a liquid phase. The condensers of the construction described (see JP-B No. 45300/1991) are called multiflow condensers, and realize high efficiencies, lower pressure losses and supercompactness.
It is required that the flat heat exchange tube be excellent in heat exchange efficiency and have pressure resistance against the high-pressure gaseous refrigerant to be introduced thereinto. Moreover, the heat exchange tube needs to be small in tubular wall thickness and low in height so as to provide compacted condensers.
Such a flat heat exchange tube is known as disclosed in JP-A No. 328773/1998. This heat exchange tube comprises flat upper and lower walls, right and left side walls interconnecting the right and left side edges of the upper and lower walls, and a plurality of reinforcing walls connected between the upper and lower walls, extending longitudinally of the tube and spaced apart from one another, the tube having parallel fluid passages formed in its interior and extending forward or rearward. The tube is formed from a lower component member of aluminum providing the lower wall, opposite side walls and reinforcing walls, and an upper component member of aluminum providing the upper wall and opposite side walls. A plurality of small projections protruding upward and arranged at a spacing in the longitudinal direction are formed on the upper surface of the lower wall at the portion thereof defining each fluid passage, i.e., at the portion between each pair of adjacent reinforcing walls. The reinforcing wall has a plurality of communication holes arranged at a spacing longitudinally thereof for holding the parallel fluid passages in communication with one another therethrough.
With the condenser comprising such flat heat exchange tubes, communication holes are formed in the reinforcing walls, so that the portions of refrigerant flowing through the respective parallel passages flow transversely of the heat exchange tubes through the communication holes, spreading over all the passages and becoming mixed together to eliminate the likelihood of a temperature difference occurring in the refrigerant between the fluid passages. This results in an improved heat exchange efficiency.
At the location where the refrigerant in the form of a liquid is present conjointly with the refrigerant in the form of a gas, the liquid refrigerant flows so as to form a liquid film over the upper surface portions of the lower wall defining the respective fluid passages, making it less likely that the gaseous refrigerant will come into contact with the upper surface of the lower wall, whereas the projections formed on the lower wall upper surface disturb the flow of the liquid refrigerant, thereby causing the gaseous refrigerant to come into direct contact with the lower wall upper surface to attain an improved heat exchange efficiency.
However, a still higher heat exchange efficiency is required of condensers in recent years, and the condensers comprising conventional heat exchange tubes fail to fully meet this requirement.
An object of the present invention is to overcome the above problem and to provide a flat heat exchange tube for realizing a heat exchanger which is further improved in heat exchange efficiency.
The present invention provides a flat heat exchange tube which comprises an upper wall, a lower wall, right and left side walls interconnecting right and left side edges of the upper and lower walls, and a plurality of reinforcing walls connected between the upper and lower walls, extending longitudinally of the tube and spaced apart from one another, the tube having parallel fluid passages formed inside thereof and extending forward or rearward, each of the reinforcing walls having a plurality of communication holes arranged at a spacing longitudinally thereof for holding the parallel fluid passages in communication with one another therethrough, an upper surface of the lower wall being provided at a portion thereof forming each of the fluid passages with a plurality of turbulence producing portions extending over the entire width of the fluid passage and arranged at a spacing longitudinally of the passage.
At the location where the refrigerant in the form of a liquid and the refrigerant in the form of a gas are present as mixed together in a condenser comprising such flat heat exchange tubes, the flow of liquid refrigerant forming a liquid film over the upper surface of the lower wall is greatly disturbed by the turbulence producing portions on the upper surface of the lower wall, consequently permitting the gaseous refrigerant to come into contact with the upper surface of the lower wall with greater ease than is the case with the conventional projections. This enables the condenser to achieve a higher heat exchange efficiency than those wherein conventional flat heat exchange tubes are used.
With the flat heat exchange tube according to the present invention, the communication holes in the reinforcing walls are in a staggered arrangement when seen from above, and the turbulence producing portions include those each having one end positioned in corresponding relation with a front end of the communication hole formed in one of the adjacent reinforcing walls and the other end positioned in corresponding relation with a rear end of the communication hole formed in the other reinforcing wall and positioned immediately to the front of the communication hole in said one reinforcing wall, and those each having one end positioned in corresponding relation with a rear end of the communication hole formed in said one reinforcing wall and the other end positioned in corresponding relation with a front end of the communication hole formed in said other reinforcing wall and positioned immediately to the rear of the communication hole in said one reinforcing wall.
In the case of the flat heat exchange tube according to the present invention, the communication holes in the reinforcing walls are in a staggered arrangement when seen from above, and the turbulence producing portions alternatively include those each having one end positioned in corresponding relation with a front end of the communication hole formed in one of the adjacent reinforcing walls and the other end positioned in corresponding relation with a front end of the communication hole formed in the other reinforcing wall and positioned immediately to the rear of the communication hole in said one reinforcing wall, and those each having one end positioned in corresponding relation with a rear end of the communication hole formed in said one reinforcing wall and the other end positioned in corresponding relation with a rear end of the communication hole formed in said other reinforcing wall and positioned immediately to the rear of the communication hole in said one reinforcing wall.
The present invention provides another flat heat exchange tube which comprises an upper wall, a lower wall, right and left side walls interconnecting right and left side edges of the upper and lower walls, and a plurality of reinforcing walls connected between the upper and lower walls, extending longitudinally of the tube and spaced apart from one another, the tube having parallel fluid passages formed inside thereof, an upper surface of the lower wall being provided at a portion thereof forming each of the fluid passages with a plurality of turbulence producing portions extending straight rearward as inclined leftward or rightward and arranged at a spacing longitudinally of the tube.
At the location where the refrigerant in the form of a liquid and the refrigerant in the form of a gas are present as mixed together in a condenser comprising such flat heat exchange tubes, the flow of liquid refrigerant forming a liquid film over the upper surface of the lower wall is greatly disturbed by the turbulence producing portions formed on the upper surface of the lower wall and extending straight rearwardly leftward or rightward, consequently permitting the gaseous refrigerant to come into contact with the lower wall upper surface with greater ease than is the case with the conventional projections. This enables the condenser to achieve a higher heat exchange efficiency than those wherein conventional flat heat exchange tubes are used.